Slow RPM Alternator?

I want to generate electricity for small batteries (maybe 16 amp hours needed) with pedal power, from a bicycle. And I need advice about what kind of generator to use.

Is it possible to get more electricity from a wide generator? Like something made for wind power?I watched a video about how to turn a ceiling fan into an alternatorâ€¦.but have nothing to compare it to.

Need more information. 16 amp-hours at what voltage? And how long can you take to charge them?

For your second post, with a 13 tooth driven sprocket (you said 12-14) the output would spin at 1761 rpm. This is a 29:1 ratio, so the rider would have to exert 29x the torque required by the generator.

As for why bother, only you can determine if it makes sense. Your losses shouldn't be as bad as 50%, though, depending on the drive design.

If you are building your own it will be very difficult to build a small diameter unit.

If you charge a battery at 10Watt/hours, yoo can be sure that you lost a good amount more than that to inefficiencies. Some are in the generation (I^2R heating), quite a lot is lost in the chemical reactions in the battery itself.

It is common to charge a capacitor and light an LED with that for some light when stopped.

If you go to a prop in the wind the inefficiency is much greater. The best wind turbines are around 40% efficient, you won't come close to that on your own. Much better to take the power directly from the hub or wheels.

As part of our senior project in school, we wanted to add a generator to a human powered vehicle. We had our generator positioned on the main chain in between the crankset and the rear cassette. We also had a voltage amplifier to help us out at slower cruising speeds. I'm not the one who did the design work on it (my main task was the roll cage and frame) but we were only powering large capacitors and LED lights.